Electrical element



July 26, 1932. J. s. TIMMONS ELECTRICAL ELEMENT Filed Aug. 16, 1929 2Sheets-Sheet "1 July 26, 1932. J. 5. TiMMoNs ELECTRICAL ELEMENT 2Sheets-Sheet 2 Filed Aug. 16, 1929 Patented July 26, 1932 UNITED STATESPATENT OFFICE JOHN S. TIMMONS, OF WYNCOTE, PENNSYLVANIA, ASSIGNOR T0PHILADELPHIA STOP: AGE BATTERY COMPANY, OF PHILADELPHIA, PENNSYLVANIA, ACORPORATION OF PENNSYLVANIA ELECTRICAL ELEMENT Application filed August16,1929. 'Serial No. 386,382.

This invention relates to improvements in sound reproducers of theso-called electrodynamic type, and relates more particularly toimprovements in the construction of the voice coil of such speakers.

In sound reproducers of the electrodynamic type, a diaphagm is actuatedthrough the medium of a coil wire attached to the diaphragm and freelysuspended in a magnetic field, the variable voice currents being appliedto the coil and causing it to move in the magnetic field. It isdesirable that the coil shall have the characteristics of stiffnesslightness of weight and thinness, and should be so constructed that itis not liable to change its shape under varying conditions oftemperature and humidity.

It is the principal object of the present invention to provide a voicecoil of novel con struction having in marked degree the aforesaiddesirable characteristics.

The invention also contemplates the provision of a voice coil of extremesimplicity of construction capable of being manufactured easily andcheaply, and the invention also resides in the novel method ofmanufacture.

A further object of the invention is to provide simple, inexpensive andhighly eflicient means for attaching the coil to the diaphragm.

Still another object of the invention is to provide a foundation for thecoil which also includes novel means for attaching the coil to thediaphragm.

In the attached drawings:

Fig. 1 is a view in perspective of a cone diaphragm equipped with a coilfoundation made in accordance with my invention;

Fig. 2 is a view in perspective of the blank from which the voice coilfoundation is made;

Fig. 3 is a section on the line 33, Fig. 1;

Fig. 4 is a view in perspective of the diaphragm with the finished coil;

Fig. 5 is an enlarged transverse sectional view of the coil taken on theline 5-5, Fig. 6, and

Fig. 6 is an end view of the coil.

Prior to my invention, it was general practice in forming voice coilsfor electrodynamic speakers towind the wire on a molded core or spool.or upon spools built' up of'wrappe'd paper. Both of these methods arerelatively expensive, and the finished article is relatively thick andheavy, and particularly in the case of the molded form is liableto warp.

In manufacturing voice coils in accordance with my invention, a layer ofinsulated wire is first wound directly o'n'a suitable mandrel,

a sufficient number of convolutions being placed thereon to afford acoil of desired length. Over this base coil and while still upon themandrel, we wrap a piece of strong paper or the like, this paperimmediately bee fore application to the coil being dipped in orotherwise coated with a quick-drying lacquer, 1

bakelite'solution, or other suitable cementing 7 medium preferablyhaving insulating prop erties. The paper strip preferably is. just longenough to make one complete turn around the initial or base coil, andafterapplication, the wire, passed between the ends of the paper strip,is wound upon the outer sur'-' face, "thereby forming a double coil thelayers of which are separated by the paper; By reason of the use of thelacquer orother cementing agent, both the base and outer coils arecaused to adhere to the paper foundation, thus affording aself-sustaining coil which may readily be slipped from the mandrel. Theentire coil may then be further insulated and' unified if'necessar'y bydipping it intoan insulating lacquer or other suitable substance.* Sucha coil is shown in Figs. 4, 5 and e 6, in which the paper or otherfoundation is designated by the reference numeral 1, the inner or basecoil-element by 2, and the outer coil-element by 3.

= Some difliculty has been experienced in the past in attaching thevoice coil to the dia phragm in an eificient manner. In general, therequirements for such attaching means are that it shall be light andstrong and shall interfere to a'minimum degree with the physicalcharacteristics of the diaphragm. It should also be adaptable todifferent types of diaphragm'su'ch as conical and flat. In accordancewith the present invention,the attaching means is made an integral partof the coil foundation. this device meeting all I a series of transverseslits 4 which preferably are of such length as to leave sufficient ofthe blank uncut to afford an ample solid foundation for the coils. 7

Following formation of the coil as described above, the tongues 5 formedby the, slits 4 are brought into contact with the diaphragm, the saidtongues lying flat against the surface of the latter and being securedthereto by adhesive in a manner readily un- V derstood by reference'toFigs. 1 and 3. In

this manner, the cylindrical foundation and the coil-elements associatedtherewith are secured to the diaphragm with uniform strength around theentire circumference. The leads 6 and 7 from the wound coil or coils maybe passed under or between the tongues 5 and are thereby secured inpos1- tion.

While the coil foundation is illustrated herein as applied to a conediaphragm, it

- will be apparent that by spreading the whole. V

tongues 5 at right angles'to the rest of the blank, the foundation mayas readily be attached to diaphragms of the disk type. In I fact,thedevice in principle is adaptable to diaphragms of practically anyform. V A voice coil made as set forth above has been found to possessin marked degree all the desirable characteristics outlined, isrelatively inexpensive to manufacture, and may be readily and rigidlyapplied to the dia phragm. The coil also has the advantage of insulationin the form'of the paper strip between the concentric coil-elements. Theadvantage of lightness in a coil of this class will be apparent; 'Byproviding a coil that is rigid and not subject to warping, the gap erscomprising a thin substantially annular strip and a continuous coil in aplurality of layers, two of which layers respectively engage the innerand outer faces of said annular strip, said strip extending beyond oneend of the coil to constitute vmeans for operatively connecting the coilto a diaphragm.

7 JOHN S. TIMMONS.

in which the voice coil operates can be re- 7 duced safely to a minimum,thereby increas-. ing the strength of the magnetic field in which thecoil operates and correspondingly lncreasing the efiiciency of thedevice as. a

I claim: I a

V 1 A voice coil for electrodynamic speakers comprising a thinsubstantially annular stripand a continuous coil in two layersrespectlvely engaging the inner and outer faces of said annular strip,said strip extending beyond one end of the coil to constitute means foroperatively connecting the coil to a diaphragm.

2. A voicecoil for electrodynamic speak-.

